I haven't seen any indication of how widespread the problem might be, there's still nothing on the official Gmail blog. The blog on July 9th...http://gmailblog.blogspot.com/2015/0...-you-dont.html
...does brag about "Now, we are bringing the same intelligence developed for Google Search and Google Now to make the spam filter smarter in a number of ways." So that's probably the culprit.